Headlines about “new battery technology” are more frequent because of renewable energy, electric vehicles and energy storage for the power grid. Actually, such headlines have been commonplace for some time. Of course, this is not to contend that MIT scientists haven’t developed a battery that will allow charging in 10-30 seconds. The real issue is that the headline rarely tells the whole story.
Quite simply, no battery technology has ever become commercially successful based on a single metric. A battery or cell is an electrochemical system with a very complex system of tradeoffs. Optimize or maximize one parameter and likely another one (or two or more) will suffer. Important performance parameters that tend to work against one another as tradeoffs are energy density, charge rate, discharge rate, cycle life, calendar life, high-temperature stability, low-temperature performance, abuse tolerance and safety. Targeting an application’s requirements and striking the right balance with cell chemistry to meet those requirements are what transforms a good “lab technology” into a successful commercial one.
Then there are practical considerations, the latest headlines notwithstanding. Fast charging is generally a desirable trait, but the practical discussion must focus on the charger and associated circuitry in the battery pack. Fast-charging lithium ion (Li-ion) technology has existed for some time now, with lithium iron phosphate technically being able to charge in about 10 minutes.
What many designers came to recognize after this technology became available was the reality of the cost of the higher power charger needed to achieve this charge time. In addition, designers had to acknowledge that additional costs linked to the required “beefed-up” battery management system (BMS) made this technology impractical, cost-prohibitive or both.
Consider the all-electric Nissan LEAF. Its battery is reported to be a 24-kilowatt hour (24 kWh) unit — one of the smaller batteries in the coming wave of electric vehicles. To charge this battery in 30 minutes would require a power supply capable of delivering nearly 50 kilowatts of power. That is just not the kind of power delivered from a typical household electrical outlet.
Nissan is offering LEAF buyers a “home assessment” to determine if a house is equipped to handle some type of 220V charging station from Nissan (details not available yet) that will charge their battery in 4 to 8 hours. To charge that same battery to 80% in ~30 minutes, Nissan is installing “quick charge” stations in select locations around the United States.
Given the challenges that a 30-minute charge presents with special infrastructure required, it is difficult to foresee a system capable of charging a battery in 30 seconds as practical soon.
That should be tomorrow’s headline.
About the Author
Chris Turner contributes nearly 20 years of multi-disciplined battery industry experience to the strategic development of portable power solutions at ICCNexergy. In his current role, Chris assists ICCNexergy customers with battery designs particularly in the areas of cell technology evaluation, supplier evaluation, and cell selection pertaining to a wide variety of industrial, medical, data storage, and military applications.
